# Can high barometric pressure supplement low gravity?

1. Oct 20, 2016

### Gary0509

I was thinking about writing a novel where the setting takes place on a planet with a gravity similar to Mars or even the moon (Luna). My thought was that if the atmosphere was dense enough wouldn't that act in a similar fashion to increased gravity?

2. Oct 20, 2016

### Staff: Mentor

Two questions come to mind...

1) with a low gravity, where does the high barometric pressure come from?

2) with high pressures on Earth, say 100 meters below the surface of the ocean, do you weigh any more than you do near the surface?

3. Oct 20, 2016

### CWatters

No it wouldn't. There is effectively a thin layer of air between your feet and the ground. The air in that thin layer is at the same increased pressure and pushes in all directions including upwards. So increasing atmospheric pressure slightly produces no net force on the object/people.

However If you increase air pressure enough to effect the density of the air then you also change the buoyancy effect. For example (taking this to extreme) objects are more likely to float in liquid nitrogen then in gaseous nitrogen. eg the exact opposite effect to what you wanted .

Your idea only works for something like a rubber sucker stuck to a horizontal glass plate. These stick because there is a vacuum or partial vacuum between the sucker and the glass - so the increased air pressure only acts on one side.

4. Oct 20, 2016

### Staff: Mentor

If the atmosphere is so dense that it condenses into water (or something more dense than water), then yes you could float.

5. Oct 20, 2016

### Staff: Mentor

But that would be anti-gravity. The OP wants extra gravity

6. Oct 20, 2016

### Staff: Mentor

Whoops, I missed that

7. Oct 20, 2016

### Staff: Mentor

LOL

8. Oct 20, 2016

### Gary0509

So because atmospheric pressure is the same on all sides it equalizes. If it was an astronaut's lab that was in a non-terrestrial ocean, the weight of the ocean wouldn't supplement gravity. It would just make it easier to keep it pressurized to Earth standard. If he exits the lab in a space/swimsuit he'd still float or sink based upon the density of the fluid, but the pressure wouldn't alter the effect of gravity.

I think I'm getting this right. Yes?

9. Oct 20, 2016

### newjerseyrunner

Seems to be a moot point now since it won't work, but I don't see why a smaller planet couldn't have very high pressure. I'm sure there must be a theoretical limit based on the mass of the planet, but Earth certainly isn't near that limit. Venus is about the same size and has rediculously high pressure. Little Titan has atmospheric pressure on the surface about 1.5 time that of earth.